I have experience with making survival games maps, even if I haven't posted any, and the main, horrible problem with this is not enough land. I totally respect the cornucopia, where you have to swim to get to it, but the main problems are these:
1) There is not enough land to chase people on, the only thing I can see will help with that is giving more fishing rods, but
2) Using so much water in the arena, you can't really put any fishing rods anywhere, because that would give that certain player infinite food. And, . . .
3) It is almost impossible to have a player roaming around without at least 1 career (over powered player, term from the book) seeing them and chasing them down, which leads, again, to the first problem. There needs to be more things that people can hide behind, so that at least this game lasts for 20 minutes.